The present invention relates to a method for fabricating a semiconductor device, and more particularly, to a method for fabricating a magnetic tunnel junction (MTJ) cell.
Recently, as semiconductor devices become highly integrated, a magnetic random access memory (MRAM) has attracted a good deal of attention as a next generation high performance non-volatile semiconductor memory device. The MRAM includes a transistor performing a switching operation, and an MTJ cell for storing data. The MTJ cell includes a magnetic tunnel junction unit including an insulation layer between two ferromagnetic layers. The electric resistance of the MTJ cell is changed according to the magnetization direction of the two ferromagnetic layers. Using voltage change or current change according to the resistance change, it can be determined which logic level (i.e., “1” or “0”) the data stored in the MTJ cell has.
FIG. 1 illustrates a cross-sectional view of a typical MTJ cell on which an etch byproduct is deposited. FIG. 2 illustrates a micrographic view of a typical MTJ cell on which an etch byproduct is deposited.
Referring to FIGS. 1 and 2, an anti-ferromagnetic layer 12, a first ferromagnetic layer 13, an insulation layer 14, and a second ferromagnetic layer 15 are sequentially formed over a first electrode 11. The anti-ferromagnetic layer 12, the first ferromagnetic layer 13, and the second ferromagnetic layer 15 are formed of metal compounds.
Then, a second electrode 16 is formed over the second ferromagnetic layer 15. Using the second electrode 16 as an etch barrier, the second ferromagnetic layer 15, the insulation layer 14, the first ferromagnetic layer 13 and the anti-ferromagnetic layer 12 are sequentially etched to form an MTJ cell. Here, the second ferromagnetic layer 15 and the first ferromagnetic layer 13 are separated electrically by the insulation layer 14 so that the MTJ cell operates normally.
However, the typical method for fabricating the MTJ cell may produce a conductive etch byproduct during etching, as represented by circle “A” in FIGS. 1 and 2, thereby deteriorating electric property of the MTJ cell. The metal compounds constituting the anti-ferromagnetic layer 12, the first ferromagnetic layer 13 and the second ferromagnetic layer 15 have high boiling points. Accordingly, the conductive etch byproduct 18 produced during the etching of the metal compounds is evaporated, but then redeposited on the side wall of the MTJ cell. The conductive etch byproduct 18 redeposited on a sidewall of an MTJ unit 17 can short the first ferromagnetic layer 13 and the second ferromagnetic layer 15, deteriorating the electric property of the MTJ cell. This may cause a fail in a semiconductor device, such as an MRAM, to which the MTJ cell is applied, decreasing reliability and FABRIC yield of the semiconductor device. The conductive etch byproduct 18 deposited on the sidewall of the MTJ unit 17 is produced during the etching of the anti-ferromagnetic layer 12. Accordingly, there is a need for a method for preventing the deterioration of the electric property of the MTJ cell caused by the conductive etch byproduct 18 produced during the etching of the anti-ferromagnetic layer 12.